private bool HandshakeServer(SymServer symServer)
{
try
{
if (symServer == null)
{
return(false);
}
symServer.IsInUse = true;
//var client = _symConnectionList[symServer.Id];
var client = _symConnectionList.Find(symConn => symConn.Id == symServer.Id).TcpClient;
// open if not already open
if (!client.Connected)
{
client.Connect(symServer.Host, symServer.Port);
}
// send/rcv buffers
var req = Encoding.ASCII.GetBytes("HANDSHAKE\n");
var resp = new byte[_maxbuffersize];
// send handshake
var socket = client.Client;
socket.Send(req);
// get & validate response
socket.Receive(resp);
var handshakeResponse = Encoding.ASCII.GetString(resp).Replace("\0", "").Replace("\n", "").Trim(); //trim nulls and control chars;
if (handshakeResponse.StartsWith("RSHANDSHAKE"))
{
// good response
symServer.IsInUse = false;
return(true);
}
// bad response; leave host out of pool
return(false);
}
catch (SocketException s)
{
if (s.ErrorCode == 10061) // refused; connection not open or in use
{
// take server out of rotation
symServer.IsFaulted = true;
return(false);
}
// take server out of rotation
symServer.IsFaulted = true;
return(false);
}
}
/// <summary>
/// Asyncronously fetch our next symServer from the list
/// </summary>
/// <returns></returns>
private async Task <SymServer> AcquireNextHost()
{
int attempts = 0;
//set a task completion source and a timer, attempt to re-acquire our socket every
TaskCompletionSource <SymServer> tcs = null;
SymServer acquiredServer = null;
//set timer for retry interval on send
var t = new System.Timers.Timer()
{
AutoReset = true, Enabled = true, Interval = _retryInterval
};
//create task completion source loop
tcs = new TaskCompletionSource <SymServer>(t);
t.Elapsed += (sender, e) =>
{
var senderTimer = sender as System.Timers.Timer;
lock (_acquireSocketLock)
{
acquiredServer = GetNextHost();
}
attempts++;
if (acquiredServer != null || attempts > _maxRetries)
{
senderTimer.Close();
if (!tcs.TrySetResult(acquiredServer))
{
System.Diagnostics.Debug.WriteLine("Failed to set result for host acquisition");
}
}
};
//activate our timer
t.Start();
//await our task result
return(await tcs.Task);
}
private void UnlockHost(SymServer host)
{
// unlock server
host.IsInUse = false;
}